Mixers



Sept. 24, 1963 P. AUGUST ETAL MIXERS Filed Feb. 8, 1961 IN VE N TORS PAUL AUGUST HVGEBQRG AUGUST BJWWILW Attorneys both of Directorio 130, Argentina The present invention concerns a device for mixing concrete, bitumen or other substances, agitated by blades with the addition of a liquid in counterflow positive mixing.

An object of the present invention is :to carry out this mixing process, and to design the mixer used for this purpose in such a way as to enable the thorough mixing within a short time even of substances with very different specific weights, while producing a cheap and easily manufactured device which is, moreover safe in operanon.

It is a further object of the invention to design the mixing device in such a way that the supply of material to be mixed is effected as a function of the amount of material present in the mixer.

There are already known mixing devices. Some of these known devices use flows of mixing material, partly also in opposite directions. However, with these known devices, there is no guarantee that the various flows of material are really mixed, so that it may be ensured with certainty that the material carried in one direction reaches in part or in its entirety the material carried in the other direction.

The present invention has the object of eliminating these drawbacks and to eifect the mixing in such a man ner that the entire material is thoroughly mixed in a short time and by means of a reliably operating device, and that the material introduced in the various directions is diverted effectively into other directional flows.

According to the present invention, a device for mixing materials such as concrete, in a mixing trough, in which mixing tools with mutually differing pitches are arranged concentrically on a common shaft, is characterized in that the material is adapted to be conveyed due to the position of the blades from the end wall of the mixing trough towards the center and by a divided screw conveyor from the center.

The point at which the blades reverse the direction of conveying are preferably offset relative to the reversing points of the paddle worm conveyors, so that the resulting four mixing zones are mutually oifset.

Preferably, the blades are arranged on the periphery and near the planes of the front walls, while the paddle worm conveyor is located near the shaft.

The design of the mixing zones and the appropriate arrangement of the blades on the outside and of the paddle worm conveyor on the inside results in a considerably better mixing within a shorter time.

With the new device, the material is located in the bottom of the trough and is carried from there towards the mixing shaft to within the zone of the screw. There is no continuous conveying of the material without mixing. Since also the points of intersection of the four zones in the mixer are offset relative to one another, the distribution of the material is uneven, so that the mix must be conveyed only over a very short distance. Consequently, the required mixing time is short.

The internally positioned screw, which is connected to the shaft, preferably reinforces statically the buckling point located approximately in the center point of the shaft, preventing even mixing shafts of comparatively light construction from sagging. The mixing shaft which, as is known, must carry the entire weight of the mixing drum and of the mix, is thereby rendered stronger, without, however, necessitating more material or becoming heavier. Since the internal mixing screw is practically free from wear, it may even be combined with the shaft by continuous welding to form a static carrying body therewith. The peripherally located blades scrape along the wall of the trough and are, therefore, subject to wear; for this reason they must be easily exchangeable. This is effected by assembling these blades by means of bolts and by designing them as individual components. Only the continuous screw on the inside and the exchangeable blades on the outside are necessary.

The position of the blades is so selected that the mix is conveyed from the front walls towards the center. Somewhere near the center or directly in the center, the material accumulates and is forced towards the inner zone. From this inner zone it is again carried towards the outside by the paddle screw system. Since the paddle screw system is offset relative to the inter-section of the blade system, one part of the material goes towards the left and the other part towards the right, so that there results a positive mixing action.

The internal continuous screw entails a static strengthening of the entire shaft. Consequently, the bearings and other components may be lighter. The shaft is also strengthened against bending by this internal screw. Furthermore, this latter feature results in a considerably lighter construction of the mixer.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 shows diagrammatically the interior of a mixing trough with the screw conveyors and blades, and with the bearings;

FIG. 2 is a side elevation of the device of FIG. 1 and shows the charging aperture.

In FIG. 1 there is shown a mixing trough 1, having a filler aperture 2. This mixing trough 1 is mounted on a rotating shaft 3, lateral bearings 4, 5 being mounted on a frame 6, as known per se. The shaft 3 is driven by means of a chain wheel 7. On the rotating shaft 3, there are mounted supports or braces 8, which pass therethrough and may have shorter ends Fitted to these supports are mixing devices in the form of scoops or blades 10 which are preferably mounted on tubes 11 which are pushed over the supports 8 and fixed thereto. By appropriately positioning the blades 10, they will convey the material on the left-hand side of the mixing trough 1 in the direction of the arrow 12 and on the right-hand side in the direction of the arrow 13. These two conveying directions are reversed at the line 14 shown in FIG. 1.

Mounted on the supports 8 or on the shaft 3', there are also fitted additional mixing devices such as conveyor screws or paddle worms 15 in the form of helical bands. 'Ihese screws consist of a longer portion, formed by a screw part 16, and a shorter portion 17, conveying in the opposite direction. The point of reversal of these two conveying directions is shown by a dotted line 18, that is, the smaller screw section 17 conveys in the direction of the arrow 20 and the longer screw section 16 in the direction of the arrow 19, namely in each case from the center towards the front or end walls 21, 22. It may be seen that the points of reversal of the blades and the screws, indicated by the positions of lines 14 and 18, overlap by an amount shown by a distance 23 in the middle portion of the trough. There results, therefore, a quick and thorough mixing, both within the two mixing zones where mixing is effected in counterflow, and within the overlap zone. The materials to be mixed, which are placed into the trough as indicated by the arrows 26, may therefore be again extracted after a short period of time.

' 9 as Naturally, this method may be equally well appiled to a continuous mixer, that is, to an appliance where the materials are placed into the mixer from one end Wall, and extracted through the other. In this case the appropriate sloping position of the .mixing drum or mixing trough 1 must be provided. The blades are spaced from the end Walls 21, 22 at a distance 27 and from the mixing trough 1 at a distance 28; these distances are sufficient to prevent concrete from adhering to the walls of the trough. Deflector rings '29 arranged adjacent to the bearing supports 30 serve to throw off any escaping mix or liquid. These bearing supports 30 are so shaped that there is a gap between the end walls and the bearing, and that the bearing support is open towards the bottom.

What we claim is: 1. Apparatus for mixing materials such as concrete in a cylindrical mixing trough, said apparatus having an while those that are remote from the shafit are in the form of scoops.

3. The apparatus of claim, 2, in which the scoops are mounted on radial arms.

4. The apparatus of claim 2, in which the helical bands have difierent dimensions so as to' move different portions of the material at different speeds.

5. The apparatus of claim 2, in which the helical bands comprise two sections of different lengths and with reopening for receiving material comprising a rotary shaft protruding through said trough from one end to the other and having mounted thereon a plurality of mixing devices at different distances from the shaft, those close to the shaft being inclined in opposite directions to move the material away from its place of reception near the center towards the ends of the trough While those remote from the shaft being inclined to move the material from the ends of the trough toward a meeting place near the center of the trough, the meeting place being axially ottset from the place of reception so that the receiving and approaching portions of the material will overlap each other in the middle portion of the trough.

2. The apparatus of claim 1, in which the mixing devices that are close to the shaft comprise helical bands verse pitches for moving the material in opposite directions in the two halves of the trough.

6. The apparatus of claim 3, in which at each end of the drum there is an outer scoop on one end of a radial arm carried by the shaft and also another scoop on the other end of the arm but closer to the shaft.

7. The apparatus of claim 3, in which the radial arms pass through the shaft and carry tubes for supporting the scoops. t 1

8. The apparatus of claim 2, in which the scoops that are nearest the end walls are tilted to move the material inwardly While the helical bands terminate further in from the end walls.

9. The apparatus of claim 1, in which the trough has a central opening extending lengthwise thereof, but covered near the ends of the trough.

References Cited in the file of this patent UNITED STATES PATENTS 

1. APPARATUS FOR MIXING MATERIALS IN A CYLINDRICAL MISING TROUGH, SAID APPARATUS HAVING AN OPENING FOR RECEIVING MATERIAL COMPRISING A ROTARY SHAFT PROTRUDING THROUGH SAID TROUGH FROM ONE END TO THE OTHER AND HAVING MOUNTED THEREON A PLURALITY OF MIXING DEVICES AT DIFFERENT DISTANCES FROM THE SHAFT, THOSE CLOSE TO THE SHAFT BEING INCLINED IN OPPOSITE DIRECTIONS TO MOVE THE MATERIAL AWAY FROM ITS PLACE OF RECEPTION NEAR THE CENTER TOWARDS THE ENDS OF THE TROUGH WHILE THOSE REMOTE FROM THE SHAFT BEING INCLINED TO MOVE THE MATERIAL FROM THE ENDS OF THE TROUGH TOWARD A MEETING PLACE NEAR THE CENTER OF THE TROUGH, THE MEETING PLACE BEING AXIALLY OFFSET FROM THE PLACE OF THE RECEPTION SO THAT THE RECEIVING AND APPROACHING PORTIONS OF THE MATERIAL WILL OVERLAP EACH OTHER IN THE MIDDLE PORTION OF THE TROUGH. 